Carbon black has been produced for many years by pyrolytical decomposition of hydrocarbon feedstocks, e.g., aromatic oils. One very successful known process for the production of carbon black consists in contacting normally liquid hydrocarbon feedstock with hot combustion gases produced by combusting a fuel, e.g., natural gas.
The properties of carbon black can be varied in broad ranges by adjusting several parameters of the furnace process and the reactor. Some properties of carbon black seem to be correlated so that they cannot be independently varied in a given reactor by merely adjusting adjustable parameters.
Two properties of carbon black that are inversely related seem to be tint and structure. Tint or tinting strength is a measure for the coloring power of a carbon black as compared to a standard carbon black. Different methods to determine tint experimentally have been described in the art. Today tint is determined in accordance with ASTM D 3265-73. Structure is a measure for the complexity of the carbon black particle. The more carbon black nodules are "fused" together into the carbon black aggregates, the higher the structure of such a carbon black is. The structure is determined in accordance with the ASTM method D-2414-70.
It has been found that an increase in tint lowers the structure of the respective carbon black and vice versa. This is particularly the case in tubular carbon black reactors in which a hydrocarbon feed stream is axially fed along the reactor axis and is mixed with a vortex of hot combustion gases, which is generated around the axial feed stream such as to decompose the hydrocarbon feed stream into carbon black.
It would be desirable to have a carbon black reactor available that is basically such a tubular reactor with a hot combustion gas vortex surrounding the hydrocarbon feed stream, but that is versatile enough to allow the production of carbon black with high structure and high tint.